Summary: New research finds that people who use illicit amphetamines face about a fivefold greater risk of developing psychosis.
Source: BMJ
The illicit use of amphetamines—often referred to as “speed”—is associated with a roughly fivefold increase in the risk of psychosis, according to a 10-year retrospective cohort study published in Evidence-Based Mental Health.
Researchers found this elevated risk across all age groups, with particularly pronounced effects among women and people with multiple arrests for possession. The study also suggests that participation in rehabilitation during deferred prosecution may reduce the likelihood of later psychotic episodes.
Globally, the estimated prevalence of amphetamine use is under 1%, yet about one in ten users develop dependence. Amphetamines affect neurotransmitter systems in the brain and can trigger psychotic symptoms—paranoia, hallucinations, and auditory or visual experiences that resemble schizophrenia. While many drug-induced psychotic episodes resolve within days, up to 15% of affected users can experience symptoms that persist for years.
Although the connection between amphetamine misuse and psychosis has long been observed, the precise magnitude of the risk and the extent to which rehabilitation mitigates that risk have been less clear. To address these questions, the investigators analyzed anonymized records from two nationwide Taiwanese databases covering 2007–2016: the Taiwan Illicit Drug Issue Database (TIDID) and the National Health Insurance Research Database (NHIRD).
TIDID includes anonymized demographic details, arrest records, and records of deferred prosecution linked to rehabilitation for illicit drug users. NHIRD provides anonymized clinical data for mental and physical health conditions across Taiwan’s population. From these sources the team identified 74,601 people with records of illicit amphetamine use and matched them by age and sex to 298,404 individuals without illicit-drug records. The average age in both groups was 33 years; 84% of participants were male.
At baseline, amphetamine users displayed higher rates of several health conditions compared with the non-user cohort: diagnosed depression (2.0% vs 0.4%), anxiety (0.9% vs 0.3%), ischemic heart disease (1.3% vs 0.8%), other cardiovascular disease (0.8% vs 0.45%), and stroke (1.3% vs 0.7%).
Over the 10-year follow-up, amphetamine users were more than five times as likely to be diagnosed with psychosis after adjusting for age, sex, and comorbidities. The annual cumulative incidence of psychosis was 468 per 100,000 among amphetamine users versus 77 per 100,000 in the comparison group.
New cases of psychosis appeared across all age groups, but the relative increase among amphetamine users was particularly notable in people aged 45 and older. Although the absolute risk of psychosis rose with the number of coexisting medical conditions, the elevated risk was observed even among amphetamine users without recorded comorbidities, supporting a direct role for amphetamines in provoking psychotic symptoms.
Risk also tracked with criminal justice involvement: people with more arrests for amphetamine-related offenses had higher rates of subsequent psychosis. Those arrested five or more times had more than a sixfold increase in psychosis risk. By contrast, individuals who entered rehabilitation as part of a deferred prosecution program had a reduced risk of developing psychosis—about 26% lower than users who did not undergo rehab—suggesting that treatment may help prevent later psychotic episodes.
Consistent with previous studies, illicit amphetamine use was associated with higher rates of anxiety and depressive symptoms as well as cardiovascular complications. The authors note that persistent psychotic symptoms could contribute to later cognitive decline in amphetamine users, underscoring the importance of early identification and treatment to protect cognitive function.
The study also observed stronger associations in women. The researchers propose several possible explanations: biological factors such as interactions between amphetamine effects and estrogen, and social factors including higher levels of trauma, reduced psychosocial support, and greater stigma among women arrested for amphetamine use.
As an observational, retrospective analysis, the study cannot establish causation. The databases lacked validated measures of dose, frequency, or severity of dependence, so the investigators could not quantify addiction levels or precisely measure exposure. Additionally, amphetamine use might precipitate or worsen underlying schizophrenia in some individuals; therefore, the findings can indicate induction or exacerbation of psychotic symptoms rather than definitive causation.
The authors conclude that amphetamine abuse has a long-established association with paranoid psychosis, and their large, population-based analysis provides detailed comparative evidence of increased psychosis incidence among illicit amphetamine users. They recommend further work to evaluate the health benefits and cost-effectiveness of deferred prosecution programs that combine legal measures with evidence-based addiction therapies.
The findings highlight the importance of prevention, early identification of psychotic symptoms, and access to rehabilitation for people who use amphetamines. Increasing availability of psychosocial support and ensuring timely treatment may reduce the burden of drug-related psychosis and improve long-term mental and cognitive outcomes.
About this psychosis research news
Author: Press Office
Source: BMJ
Contact: Press Office – BMJ
Image: The image is in the public domain
Original Research: Open access. “Risk of psychosis in illicit amphetamine users: a 10 year retrospective cohort study” by Chieh-Liang Huang, I-Ju Tsai, Cynthia Wei-Sheng Lee. Evidence-Based Mental Health
Abstract
Risk of psychosis in illicit amphetamine users: a 10 year retrospective cohort study
Question
Amphetamine use is a recognized risk factor for psychosis, which carries substantial societal and clinical burden. This study aimed to quantify the incidence of psychosis associated with illicit amphetamine use and to assess whether rehabilitation treatments during deferred prosecution influence that risk.
Study selection and analysis
Using the population-based Taiwan Illicit Drug Issue Database (TIDID) and the National Health Insurance Research Database (NHIRD) from 2007 to 2016, researchers conducted a retrospective cohort study. They identified 74,601 individuals with records of illicit amphetamine use and 298,404 matched comparison subjects without such records. The primary outcome was the incidence of newly diagnosed psychosis. Cox proportional hazards models were used to evaluate the effect of amphetamine exposure, and Kaplan–Meier curves estimated cumulative psychosis incidence.
Findings
Illicit amphetamine users had a 5.28-fold higher risk of psychosis compared with non-users. Risk increased with the number of arrests for amphetamine possession, and female patients showed a larger hazard ratio. Rehabilitation during deferred prosecution was associated with a significant reduction in psychosis risk (adjusted hazard ratio 0.74, 95% CI 0.61–0.89).
Conclusions
Illicit amphetamine use is linked to an increased incidence of psychosis across all ages, particularly among women and individuals with multiple arrests. Participation in rehabilitation programs was associated with a lower risk of psychosis, supporting the potential benefit of combining legal diversion with addiction treatment.